Scroll-Type Fluid Machine

ABSTRACT

To provide a scroll-type fluid machine in which the influence on power recovery efficiency of a clearance in an expansion section is reduced. A scroll-type fluid machine ( 100 ) includes: a scroll unit ( 20 ) in which a fixed scroll ( 3 ) and an orbiting scroll ( 4 ) are disposed and an expansion section ( 1 ) and a compression section ( 2 ) are formed; and a support part ( 30 ) that supports the orbiting scroll ( 3 ) so as to be able to perform revolving motion, the compression section ( 2 ) being driven by power recovered in the expansion section ( 1 ). A minimum clearance between a wrap ( 3 L) of the fixed scroll ( 3 ) and a wrap ( 4 L) of the orbiting scroll ( 4 ) in the expansion section ( 1 ) is set to be less than a minimum clearance between the wrap ( 3 L) of the fixed scroll ( 3 ) and the wrap ( 4 L) of the orbiting scroll ( 4 ) in the compression section ( 2 ).

TECHNICAL FIELD

The present invention relates to a scroll-type fluid machine, and more specifically, relates to a scroll-type fluid machine suitable for use as a compressor-integrated expander.

BACKGROUND ART

As a conventional scroll-type fluid machine, for example, a scroll-type fluid machine disclosed in Patent Document 1 is known. The scroll-type fluid machine disclosed in Patent Document 1 is provided with an orbiting scroll in which a volute wrap is formed, a fixed scroll in which a volute wrap which is engaged with the wrap of the orbiting scroll is formed, and a support part that supports the orbiting scroll so as to be able to perform revolving motion with respect to the fixed scroll, and the scroll-type fluid machine is configured so as to form a compression section and an expansion section by partitioning a working chamber between the volute wrap of the fixed scroll and the volute wrap of the orbiting scroll by a partition wall.

The scroll-type fluid machine is connected to, for example, a refrigeration circuit, drives the orbiting scroll to move around in a revolving manner by the expansion energy of a high-pressure working fluid introduced from the refrigeration circuit into the expansion section, compresses a low-pressure working fluid introduced from the refrigeration circuit into the compression section by the revolving drive force, and discharges the compressed working fluid to a main compressor separately provided on the refrigeration circuit side. In this way, power is recovered by expanding the working fluid and the working fluid is compressed by using the recovered power.

REFERENCE DOCUMENT LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-open Publication No. 2012-52527

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Here, in this type of scroll-type fluid machine, as described above, in a case in which power is recovered by expanding the working fluid and the working fluid is compressed by using the recovered power, since an expansion ratio in the expansion section is high, the influence on power recovery efficiency of a seal portion clearance (hereinafter referred to as a “minimum clearance”) between the wrap of the orbiting scroll and the wrap of the fixed scroll in the expansion section becomes large, and thus, there is a concern that the power recovery efficiency may be adversely affected.

The present invention has been made in view of such a problem and has as an object to provide a scroll-type fluid machine in which the influence on power recovery efficiency of a minimum clearance in an expansion section is reduced.

Means for Solving the Problems

For this reason, according to an aspect of the present invention, there is provided a scroll-type fluid machine including: a scroll unit in which a fixed scroll and an orbiting scroll, each having a volute wrap formed therein, are disposed with the wraps facing each other, and in which an expansion section for expanding a working fluid and a compression section for compressing a working fluid are formed between the volute wrap of the fixed scroll and the volute wrap of the orbiting scroll; and a support part that supports the orbiting scroll so as to be able to perform revolving motion with respect to the fixed scroll, the compression section being driven by power recovered in the expansion section, wherein a minimum clearance between the wrap of the fixed scroll and the wrap of the orbiting scroll in the expansion section is set to be less than a minimum clearance between the wrap of the fixed scroll and the wrap of the orbiting scroll in the compression section.

Effects of the Invention

According to the scroll-type fluid machine according to an aspect of the present invention, the minimum clearance between the wrap of the fixed scroll and the wrap of the orbiting scroll in the expansion section is set to be less than the minimum clearance between the wrap of the fixed scroll and the wrap of the orbiting scroll in the compression section, and therefore, in the scroll-type fluid machine that compresses a working fluid by using the expansion energy of the working fluid, it is possible to reduce the influence on power recovery efficiency of the minimum clearance in the expansion section having a large expansion ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a scroll-type fluid machine in an embodiment of the present invention.

FIG. 2 is a plan view of a fixed scroll according to the embodiment as viewed from an orbiting scroll side.

FIG. 3 is a plan view of an orbiting scroll according to the embodiment as viewed from a fixed scroll side.

FIG. 4 is a perspective view of an eccentric bushing according to the embodiment.

FIG. 5 is a cross-sectional view illustrating a combined state of the orbiting scroll and the fixed scroll on an expansion section side according to the embodiment.

FIGS. 6A and 6B are views illustrating the minimum clearance in a radial direction of a scroll unit illustrated in FIG. 5, wherein FIG. 6A is a partially enlarged view of a portion A illustrated in FIG. 5, and FIG. 6B is a partially enlarged view of a portion B illustrated in FIG. 5.

FIG. 7 is a view illustrating the combined state of the orbiting scroll and the fixed scroll in an expansion section according to the embodiment, and is a partial longitudinal sectional view of the portion A illustrated in FIG. 5.

FIG. 8 is a view illustrating the combined state of the orbiting scroll and the fixed scroll in a compression section according to the embodiment, and is a partial longitudinal sectional view of the portion B illustrated in FIG. 5.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a compressor-integrated expander 100, which is a first embodiment of a scroll-type fluid machine with the present invention applied thereto.

In FIG. 1, the compressor-integrated expander 100 is connected to a refrigeration circuit (evaporator and condenser) (not shown), drives an orbiting scroll to move around in a revolving manner with respect to a fixed scroll by the expansion energy of an introduced high-pressure refrigerant, compresses a low-pressure refrigerant introduced from the refrigeration circuit by the generated turning drive force, and discharges the compressed refrigerant to a main compressor of the refrigeration circuit. The compressor-integrated expander 100 is provided with an expansion section 1 and a compression section 2 as working chambers, and drives the compression section 2 by power recovered in the expansion section 1. The expansion section 1 and the compression section 2 will be described in detail later.

As illustrated in FIG. 1, the compressor-integrated expander 100 is provided with a housing 10. In the housing 10, a scroll unit 20 provided with a fixed scroll 3 and an orbiting scroll 4, and a support part 30 that supports the orbiting scroll 4 are mainly disposed.

The housing 10 is provided with a main frame 11 that fixedly supports the fixed scroll 3, a cap-shaped top shell 12 that closes an upper portion of the main frame 11, and a cap-shaped bottom shell 13 that closes a lower portion of the main frame 11, and is made so as to sandwich the main frame 11 between the top shell 12 and the bottom shell 13.

As schematically illustrated in FIG. 1, an expansion-side suction pipe 14 that makes a refrigerant from the refrigeration circuit flow into the expansion section 1, an expansion-side discharge pipe 15 that discharges the refrigerant expanded in the expansion section 1 toward the refrigeration circuit, and a compression-side discharge pipe 16 that discharges the refrigerant compressed in the compression section 2 toward the refrigeration circuit, are disposed in the top shell 12. The expansion-side suction pipe 14 and the expansion-side discharge pipe 15 are respectively connected to an expansion-side suction chamber 3 d and an expansion-side discharge chamber 3 e, which are formed in the fixed scroll 3, and the compression-side discharge pipe 16 is connected to a compression-side discharge chamber 12 a formed between the top shell 12 and the main frame 11. Furthermore, a compression-side suction pipe 17 which makes a refrigerant introduced from the refrigeration circuit flow into the compression section 2 is disposed on the outer peripheral portion side of the main frame 11, and the compression-side suction pipe 17 is connected to a compression-side suction chamber 3 f formed in the fixed scroll 3.

The scroll unit 20 is provided with the fixed scroll 3 and the orbiting scroll 4, in which volute wraps 3L and 4L (refer to FIGS. 2 and 3) are respectively formed and the volute wraps 3L and 4L are disposed to face each other so as to secure a minimum clearance (described later). The scroll unit 20 forms the expansion section 1 and the compression section 2 (refer to FIG. 1) configuring working chambers for a working fluid, between the wrap 3L of the fixed scroll 3 and the wrap 4L of the orbiting scroll 4.

The fixed scroll 3 is fixed to a top seating surface 11 a 1 of a stepped concave portion 11 a formed in the main frame 11, with the wrap formation surface side downward, as illustrated in FIG. 1. As illustrated in FIG. 2, in the fixed scroll 3, an inner wrap 3La and an outer wrap 3Lb as the volute wrap 3L are formed and an annular intermediate partition wall 3 a and an annular outer closer to the center side than the intermediate partition wall 3 a, and the outer wrap 3Lb is provided to be erect between the intermediate partition wall 3 a and the outer partition wall 3 b. Furthermore, in the fixed scroll 3, an annular groove 3 c (refer to FIG. 2), into which a seal ring 5 (refer to FIG. 1) is fitted, is formed in an end face of the intermediate partition wall 3 a.

Furthermore, in the fixed scroll 3, as illustrated in FIG. 2, the expansion-side suction chamber 3 d is formed at a central portion, which is an inner peripheral end of the expansion section 1, the expansion-side discharge chamber 3 e is formed at an outer peripheral end of the expansion section 1 inside the intermediate partition wall 3 a, the compression-side suction chamber 3 f is formed at an outer peripheral end of the compression section 2 inside the outer partition wall 3 b, and a compression-side discharge hole 3 g is formed to penetrate at an inner peripheral end of the compression section 2 outside the intermediate partition wall 3 a.

The orbiting scroll 4 is supported by the support part 30 so as to be able to perform revolving motion around an axis of a fixed shaft 6 (described later) while being placed on an intermediate pedestal surface 11 a 2 of the main frame 11 with the wrap formation surface side upward, in a state in which rotation is prevented by an anti-rotation mechanism 50 such as an Oldham ring. In the orbiting scroll 4, as illustrated in FIG. 3, an inner wrap 4La and an outer wrap 4Lb as the volute wrap 4L are formed. A wall surface of the inner wrap 4La faces a wall surface of the inner wrap 3La of the fixed scroll 3, a wall surface of the outer wrap 4Lb faces a wall surface of the outer wrap 3Lb of the fixed scroll 3, and the wraps 4La and 4Lb are provided to be erect in an opposing volute direction. Furthermore, as illustrated in FIG. 1, a concave portion 4 a into which an eccentric bushing 31 (described later) is inserted so as to be able to relatively rotate with respect to the orbiting scroll 4 is formed in the surface opposite to the wrap formation surface of the orbiting scroll 4.

The fixed scroll 3 and the orbiting scroll 4 are combined with each other with the wall surfaces of the wraps facing each other, as illustrated in FIG. 1, whereby the expansion section 1 is formed between the inner wrap 3La of the fixed scroll 3 and the inner wrap 4La of the orbiting scroll 4 and the compression section 2 is formed between the outer wrap 3Lb of the fixed scroll 3 and the outer wrap 4Lb of the orbiting scroll 4. In this manner, the scroll unit 20 of this embodiment is a so-called single plate type scroll unit in which the orbiting scroll 4 forming the expansion section 1 and the orbiting scroll 4 forming the compression section 2 are formed on the same surface of the same member.

The support part 30 is rotatably supported on the fixed shaft 6 and supports the orbiting scroll 4 so as to be able to perform revolving motion around an axis X1 of the fixed shaft 6. The support part 30 is specifically configured to include the eccentric bushing 31, a needle bearing 32, a radial bearing 33, and a thrust bearing 34.

The eccentric bushing 31 is rotatably supported on the fixed shaft 6 eccentrically with respect to the axis X1 of the fixed shaft 6 and is inserted into the concave portion 4 a formed in the orbiting scroll 4, so as to be able to relatively rotate with respect to the orbiting scroll 4.

Specifically, the eccentric bushing 31 is provided with a flange portion 31 a having an enlarged diameter greater than the inner diameter of the concave portion 4 a of the orbiting scroll 4, a cylindrical portion 31 b provided to be erect from the flange portion 31 a, and a balance weight 31 c integrally formed at a portion of an outer peripheral portion of the flange portion 31 a, as illustrated in FIG. 4. The cylindrical portion 31 b has a hole portion 31 d having a central axis that is eccentric with respect to an axis X3 of the cylindrical portion 31 b and coincides with the axis X1 of the fixed shaft 6, and is formed so as to be able to be assembled eccentrically with respect to the axis X1 of the fixed shaft 6. A shaft portion 6 a (refer to FIG. 1) of the fixed shaft 6 is fitted into the hole portion 31 d with the needle bearing 32 interposed therebetween, and thus the eccentric bushing 31 is rotatably supported on the fixed shaft 6. The cylindrical portion 31 b is inserted into the concave portion 4 a of the orbiting scroll 4 with the radial bearing 33 interposed therebetween. The thrust bearing 34 is disposed between the flange portion 31 a and a base portion 6 b (refer to FIG. 1) of the fixed shaft 6.

The fixed shaft 6 has the shaft portion 6 a on the upper end side, the base portion 6 b configured to be fitted into a hole portion 11 c formed to penetrate through a bottom portion of the main frame 11, and a flange portion 6 c formed to be enlarged in diameter on the lower end side, as illustrated in FIG. 1, and the shaft portion 6 a and the base portion 6 b are formed having the same axis (X1). The fixed shaft 6 is fixed to the main frame 11 with the axis X1 thereof substantially coinciding with a central axis X2 of the fixed scroll 3, for example, by fitting the base portion 6 b into the hole portion 11 c and fixing the flange portion 6 c to the lower surface of the main frame 11 by bolting or the like. That is, the fixed shaft 6 merely rotatably supports the eccentric bushing 31 and the fixed shaft 6 itself does not rotate.

In this manner, the support part 30 that includes the eccentric bushing 31, the needle bearing 32, the radial bearing 33, and the thrust bearing 34, supports the orbiting scroll 4 so as to be able to perform revolving motion around the axis X1, by making the cylindrical portion 31 b of the eccentric bushing 31, which is supported on the fixed shaft 6 through the needle bearing 32, be eccentric with respect to the axis X1 of the fixed shaft 6 and inserting the cylindrical portion 31 b into the concave portion 4 a of the orbiting scroll 4 with the radial bearing 32 interposed therebetween, so as to be able to relatively rotate with respect to the orbiting scroll 4.

Next, the minimum clearance between the wrap 3L of the fixed scroll 3 and the wrap 4L of the orbiting scroll 4 in this embodiment will be described.

As illustrated in FIG. 5, the scroll unit 20 is configured by combining the wrap 3L of the fixed scroll 3 and the wrap 4L of the orbiting scroll 4 so as to be engaged with each other. Here, it is necessary to maintain the air tightness of the expansion section 1 and the compression section 2 as the working chambers between the fixed scroll 3 and the orbiting scroll 4 during the revolving of the orbiting scroll 4, and therefore, in each of the expansion section 1 and the compression section 2, a gap in which the wrap 4L of the orbiting scroll 4 and the wrap 3L of the fixed scroll 3 most approach each other is needed to be set as small as possible. This gap is called the “minimum clearance”. An oil film for lubrication is formed in the minimum clearance (in other words, seal portion clearance), and thus each of the expansion section 1 and the compression section 2 as the working chambers is sealed.

The minimum clearance is set in each of a radial direction and an axial direction (height direction of each wrap) of the scroll unit 20. Then, a minimum clearance C in the radial direction is set on each of the expansion section 1 side and the compression section 2 side, and as illustrated in FIGS. 6A and 6B, which are partially enlarged views of a portion A and a portion B illustrated in FIG. 5, a radial minimum clearance C_(exp) on the expansion section 1 side is set to be less than a radial minimum clearance C_(comp) on the compression section 2 side. Furthermore, an axial minimum clearance CZ (that is, the clearance between the tip of the wrap and a groove bottom forming the wrap) is also set on each of the expansion section 1 side and the compression section 2 side, and as illustrated in FIGS. 7 and 8, which are enlarged longitudinal sectional views of the portion A and the portion B illustrated in FIG. 5, an axial minimum clearance CZ_(exp) on the expansion section 1 side is set to be less than an axial minimum clearance CZ_(comp) on the compression section 2 side.

In this manner, both the minimum clearances (C_(exp) and CZ_(exp)) in the radial direction and the axial direction on the expansion section 1 side are set to be less than the minimum clearances (C_(comp) and CZ_(comp)) on the compression section 2 side.

Hereinafter, the positional relationship in the radial direction between the wrap 3L (3La and 3Lb) of the fixed scroll 3 and the wrap 4L (4La and 4Lb) of the orbiting scroll 4 in the expansion section 1 and the compression section 2 will be described in detail with reference to FIGS. 4, 7, and 8.

First, the expansion section 1 side will be described. As illustrated in FIG. 7, a pitch of each of the wraps 3La and 4La of the fixed scroll 3 and the orbiting scroll 4 in the expansion section 1 is set to be P_(exp), and a wall thickness of each of the wraps 3La and 4La of the fixed scroll 3 and the orbiting scroll 4 in the expansion section 1 is set to be t_(exp). Furthermore, as illustrated in FIG. 4, an eccentric distance of the central axis (in FIGS. 4, X1 and X2) of the hole portion 31 d with respect to the axis X3 of the cylindrical portion 31 b is set to be a crank radius POR. In addition, as illustrated in FIGS. 7 and 8, the wrap 4L (4La and 4Lb) of the orbiting scroll 4 are movable by an amount corresponding to a distance of twice the crank radius POR with respect to the radial direction of the scroll unit 20 in grooves forming the wrap 3L (3La and 3Lb) of the fixed scroll 3. The crank radius POR is represented by the following Expression (1).

POR=P _(exp)/2−C _(exp) −t _(exp)  (1)

On the other hand, with respect to the compression section 2 side, as illustrated in FIG. 8, when a pitch of each of the wraps 3Lb and 4Lb of the fixed scroll 3 and the orbiting scroll 4 in the compression section 2 is set to be P_(comp) and a wall thickness of each of the wraps 3Lb and 4Lb of the fixed scroll 3 and the orbiting scroll 4 in the expansion section 1 is set to be t_(comp), the crank radius POR is represented by the following Expression (2).

POR=P _(comp)/2−C _(comp) −t _(comp)  (2)

Here, since the crank radius POR in the expansion section 1 and the compression section 2 are the same, the relational expression of the following Expression (3) is established from the above Expression (1) and Expression (2).

P _(exp)/2−C _(exp) −t _(exp) =P _(comp)/2−C _(comp) −t _(comp)  (3)

Furthermore, the relationship of the following Expression (4) is established from the above Expression (3).

C _(comp) −C _(exp)=(P _(comp)/2−t _(comp))−(P _(exp)/2−t _(exp))  (4)

Here, in order for a relationship of C_(comp)−C_(exp)>0 (that is, C_(comp)>C_(exp)) to be obtained in the above Expression (4), it is necessary to satisfy the following Expression (5).

P _(comp)/2−t _(comp) >P _(exp)/2−t _(exp)  (5)

In this manner, with respect to the radial minimum clearances (C_(exp) and C_(comp)), specifically, it is favorable if the pitches (P_(comp) and P_(exp)) and the wall thicknesses (t_(comp) and t_(exp)) are set so as to satisfy Expression (5). For example, it is favorable if the pitches (P_(comp) and P_(exp)) are made so as to coincide with each other and the wall thickness t_(exp) on the expansion section 1 side is formed thicker than the wall thickness t_(comp) on the compression section 2 side, or, the wall thicknesses (t_(comp) and t_(exp)) are made so as to coincide with each other and the pitch P_(exp) on the expansion section 1 side is formed shorter than the pitch P_(comp) on the compression section 2 side, and if the above Expression (5) is satisfied, the pitches (P_(comp) and P_(exp)) or the wall thicknesses (t_(comp) and t_(exp)) may not be made so as to coincide with each other on the expansion section 1 side and the compression section 2 side. In addition, an upper limit and a lower limit of a dimensional tolerance of each of the pitches (P_(comp) and P_(exp)) and the wall thicknesses (t_(comp) and t_(exp)) are set so as to satisfy the above Expression (5) in any dimension in the tolerance range.

Next, the positional relationship in the axial direction between the wrap 3L (3La and 3Lb) of the fixed scroll 3 and the wrap 4L (4La and 4Lb) of the orbiting scroll 4 in the expansion section 1 and the compression section 2 will be described in detail.

As illustrated in FIGS. 7 and 8, when a groove depth forming the wrap 3L (the inner wrap 3La) of the fixed scroll 3 in the expansion section 1 is set to be D_(exp), the height of the wrap 4L (the inner wrap 4La) of the orbiting scroll 4 in the expansion section 1 is set to be h_(eap), a groove depth forming the wrap 3L (the outer wrap 3Lb) of the fixed scroll 3 in the compression section 2 is set to be D_(comp), and the height of the wrap 4L (the outer wrap 4Lb) of the orbiting scroll 4 in the compression section 2 is set to be h_(comp), the relational expressions of the following Expression (6) and Expression (7) are established.

CZ _(exp) =D _(exp) −h _(exp)  (6)

CZ _(comp) =D _(comp) −h _(comp)  (7)

Here, in order for a relationship of CZ_(comp)>CZ_(exp) to be obtained from the above Expression (6) and Expression (7), it is necessary to satisfy the following Expression (8).

D _(comp) −h _(comp) >D _(exp) −h _(exp)  (8)

In this manner, with respect to the axial minimum clearances (CZ_(exp) and CZ_(comp)), specifically, it is favorable if the groove depths (D_(comp) and D_(exp)) of the fixed scroll 3 and the wrap heights (h_(comp) and h_(exp)) of the orbiting scroll 4 are set so as to satisfy Expression (8). For example, it is favorable if the groove depths (D_(comp) and D_(exp)) are made so as to coincide with each other and the wrap height h_(exp) of the orbiting scroll 4 on the expansion section 1 side is formed higher than the wrap height h_(comp) of the orbiting scroll 4 on the compression section 2 side, or, the wrap heights (h_(comp) and h_(exp)) of the orbiting scroll 4 are made so as to coincide with each other and the groove depth D_(exp) of the fixed scroll 3 on the expansion section 1 side is formed shallower than the groove depth D_(comp) on the compression section 2 side, and if the above Expression (8) is satisfied, the groove depths (D_(comp) and D_(exp)) or the wrap heights (h_(comp) and h_(exp)) may not be made so as to coincide with each other on the expansion section 1 side and the compression section 2 side. In addition, an upper limit and a lower limit of a dimensional tolerance of each of the groove depths (D_(comp) and D_(exp)) and the wrap heights (h_(comp) and h_(exp)) are set so as to satisfy the above Expression (8) in any dimension in the tolerance range.

Next, an operation of the compressor-integrated expander 100 of this embodiment will be schematically described by using FIG. 1.

A high-pressure refrigerant drawn into from the expansion-side suction pipe 14 is introduced into the expansion section 1 by way of the expansion-side suction chamber 3 d. In the expansion section 1, the volume between the scrolls 3 and 4 increases and the orbiting scroll 4 continues to perform revolving motion around the axis X1 of the fixed scroll 3 due to the expansion energy of the refrigerant. The refrigerant having served for the revolving motion of the orbiting scroll 4 is discharged toward the refrigeration circuit through the expansion-side discharge chamber 3 e and the expansion-side discharge pipe 15. On the other hand, a low-pressure refrigerant drawn into from the compression-side suction pipe 17 is introduced into the compression section 2 by way of the compression-side suction chamber 3 f. In the compression section 2, the volume between the scrolls 3 and 4 decreases due to the revolving motion of the orbiting scroll 4, and accordingly, the introduced refrigerant is compressed. Then, the compressed refrigerant is discharged toward the main compressor of the refrigeration circuit through the compression-side discharge hole 3 g, the compression-side discharge chamber 12 a, and the compression-side discharge pipe 16. In this manner, the refrigerant expands in the expansion section 1 having a large expansion ratio, and the refrigerant is compressed in the compression section 2 having a small compression ratio by using the expansion energy.

According to the compressor-integrated expander 100 of this embodiment, the minimum clearances (C_(exp) and CZ_(exp)) on the expansion section 1 side are set to be less than the minimum clearances (C_(comp) and CZ_(comp)) on the compression section 2 side, and therefore, in the scroll-type fluid machine that compresses a working fluid by using the expansion energy of the working fluid, it is possible to reduce the influence on power recovery efficiency of a clearance in the expansion section 1 having a large expansion ratio and it is possible to compress a refrigerant by efficiently recovering expansion energy.

Furthermore, in this embodiment, both the minimum clearances (C_(exp) and CZ_(exp)) in the radial direction and the axial direction on the expansion section 1 side are set to be less than the minimum clearances (C_(comp) and CZ_(comp)) on the compression section 2 side, and therefore, it is possible to perform reliable sealing in the expansion section 1. In addition, this is not limited thereto, and the minimum clearance that is set to be less in the expansion section 1 side than the compression section 2 side may be at least one of the clearances in the radial direction and the axial direction.

Then, in this embodiment, since the scroll unit 20 has been set to be a single plate type scroll unit in which the orbiting scroll 4 forming the expansion section 1 and the orbiting scroll 4 forming the compression section 2 are formed on the same surface of the same member, it is possible to make the unit compact, compared to, for example, a so-called back type scroll unit in which the orbiting scroll 4 forming the expansion section 1 and the orbiting scroll 4 forming the compression section 2 are respectively formed on separate members and the backs (that is, wrap non-formation surfaces) of the respective members are disposed to face each other.

In addition, in this embodiment, a case in which only the radial bearing 33 is provided between the orbiting scroll 4 and the eccentric bushing 31, has been described. However, this is not limited thereto, and for example, a thrust bearing may be further provided between an end face of a boss forming the concave portion 4 a and the flange portion 31 a of the eccentric bushing 31.

Furthermore, in this embodiment, a case in which the needle bearing 32 and the radial bearing 33 are provided between the eccentric bushing 31, and the concave portion 4 a and the shaft portion 6 a, has been described. However, this is not limited thereto, and the eccentric bushing 31 itself may be used as a sliding bearing receiving the mutual relative rotation of the orbiting scroll 4 and the shaft portion 6 a, without providing the bearings 32 and 33.

Furthermore, in this embodiment, the fixed shaft 6 has been described as a case of being fixed to the main frame 11 with the axis X1 thereof substantially coinciding with the central axis X2 of the fixed scroll 3, has been described. However, this is not limited thereto, and the fixed shaft 6 may be fixed with the axis X1 shifted from the central axis X2 of the fixed scroll 3.

Furthermore, in this embodiment, the support part 30 has been described as a case of having a configuration in which the support part 30 is supported on the fixed shaft 6 fixed to the main frame 11. However, this is not limited thereto, and although not illustrated, the support part 30 may be configured so as to be supported on a rotatable shaft. Furthermore, the scroll unit 20 has been described as a case of being a single plate type scroll unit. However, this is not limited thereto, and although not illustrated, the above-described back type scroll unit is also acceptable. In this case, for example, the orbiting scroll 4 forming the expansion section 1 and the orbiting scroll 4 forming the compression section 2 may be configured by a monolithic member with scrolls provided on both surfaces, and in a case of adopting separate members, a connecting shaft that connects the orbiting scrolls and transmits a rotational driving force generated in the expansion section 1 by the expansion of the working fluid to the compression section 2, may be provided.

An embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment and various modifications may be made within a scope which does not depart from the gist of the present invention.

REFERENCE SYMBOL LIST

-   100 Scroll-type fluid machine -   1 Expansion section (working chamber) -   2 Compression section (working chamber) -   3 Fixed scroll -   3L Volute wrap -   4 Orbiting scroll -   4L Volute wrap -   6 Fixed shaft -   20 Scroll unit -   30 Support part -   X1 Axis of fixed shaft -   X2 Central axis of fixed scroll 

1. A scroll-type fluid machine comprising: a scroll unit in which a fixed scroll and an orbiting scroll, each having a volute wrap formed therein, are disposed with the wraps facing each other, and in which an expansion section for expanding a working fluid and a compression section for compressing a working fluid are formed between the volute wrap of the fixed scroll and the volute wrap of the orbiting scroll; and a support part that supports the orbiting scroll so as to be able to perform revolving motion with respect to the fixed scroll, the compression section being driven by power recovered in the expansion section, wherein a minimum clearance between the wrap of the fixed scroll and the wrap of the orbiting scroll in the expansion section is set to be less than a minimum clearance between the wrap of the fixed scroll and the wrap of the orbiting scroll in the compression section.
 2. The scroll-type fluid machine according to claim 1, wherein the minimum clearance is at least one of clearances in a radial direction and an axial direction of the scroll unit.
 3. The scroll-type fluid machine according to claim 1, wherein the orbiting scroll forming the expansion section and the orbiting scroll forming the compression section are formed on the same surface of the same member.
 4. The scroll-type fluid machine according to claim 1, wherein the orbiting scroll forming the expansion section and the orbiting scroll forming the compression section are formed on separate members and wrap non-formation surfaces of the members are disposed to face each other.
 5. The scroll-type fluid machine according to claim 4, further comprising a connecting shaft that connects the orbiting scroll forming the expansion section and the orbiting scroll forming the compression section, and transmits a rotational driving force generated in the expansion section by expansion of the working fluid, to the compression section. 